Legacy Sediments Projects

[lycoflyfisher]

If there are trees in the floodplain that you are bulldozing the trees will go...

Land Studies and the folks you have mentioned from DEP all downplay any thermal benefit of shading from canopy cover. I still am not sold that all of our streams were widely braided channels in open meadow habitats.

 

[silverfox]

I still am not sold that all of our streams were widely braided channels in open meadow habitats.

I don't know anything about this stuff. Is this the consensus? That our lowlands were like that?

 

[lycoflyfisher]

I don't know anything about this stuff. Is this the consensus? That our lowlands were like that?

Among many of the key legacy sediment folks, yes.

 

[JeffP]

If there are trees in the floodplain that you are bulldozing the trees will go...

Land Studies and the folks you have mentioned from DEP all downplay any thermal benefit of shading from canopy cover. I still am not sold that all of our streams were widely braided channels in open meadow habitats.

How are lowlands defined? Lower stretches of stream? Is there a reason they wouldn't have trees? I guessb there were some meadows before man came on the scene.

 

[Fish Sticks]

Is it common to cut down a lot of trees for this kind of work? I guess I'm used to thinking these projects are on farmland.

I’m not sure if it is or not I’ve seen a few of these projects but actually never asked if trees were present. I know practioners really like shrubs as riparian buffers in these projects but I would like to see more trees because a forested wet land will have more of a temperature benefit. The reason they do this they found seeds for certain plants in the gravel basal layer after excavating down. With climate change and amphibians that rely on wetlands and cold water fish being some of most vulnerable native tree are my preference.

If there are trees in the floodplain that you are bulldozing the trees will go...

Land Studies and the folks you have mentioned from DEP all downplay any thermal benefit of shading from canopy cover. I still am not sold that all of our streams were widely braided channels in open meadow habitats.

I agree with this and given the uncertainty I say forest those wetlands, we know climate change is going to impact these sensitive herps and fish. I’m not sold either.

 

[Fish Sticks]

How are lowlands defined? Lower stretches of stream? Is there a reason they wouldn't have trees? I guessb there were some meadows before man came on the scene.

They looked at the wetland soils below the legacy sediment layer and found seeds of wetland shrubs and things of this nature but what I don’t know/need to ask is that Imagine that many of these places were deforested before/not at the same time mill dams were constructed? So based on finding seeds and shrubs from just that site, is it possible it could have been full of native tree species then deforested with secondary growth of shrubbery later on? I don’t know likely would need to talk to an arborist or a geologist or some other discipline. There is alot of uncertainty about what was there which is a shame.

 

[Mike]

If there are trees in the floodplain that you are bulldozing the trees will go...

Land Studies and the folks you have mentioned from DEP all downplay any thermal benefit of shading from canopy cover. I still am not sold that all of our streams were widely braided channels in open meadow habitats.

If we’re talking about the shade provided by immediate riparian area trees and shrubs in this case, their value in shading and cooling a stream channel, and downplaying that, one can read the papers that deal with that topic or go out with a thermometer and start seeing it with one’s own eyes. I have done that with a thermometer and just a few hundred yards of unshaded water in the summer will jack up the water temp. Likewise, more shade in my view is the primary reason why wild trout populations have expanded in SE Pa., except in the Schuylkill Co portion, where reductions in past mining effects have been primary. Perhaps one needs to have observed this for a forty+ year career to have seen it, although I saw it occur on Conowingo Ck in an eight yr period once saplings and shrubs were allowed to grow on the stream bank.

As for stream bank fencing cooling the water via the growth of tall meadow types of vegetation without the planting and growth of riparian trees and shrubs, I have not been able to discern a temperature benefit when measuring temps in the field. Better temps were not their purpose, but it was still interesting to see if the vegetation, including overhanging plants, helped.

 

[moon1284]

I know a decent amount about sediment removal, but not a whole lot about legacy removals.

In order to dredge sediment from a creek you definitely need to remove trees for access. In my line of work you typically have to plant native trees and shrubs when you're done. Obviously these trees are usually smaller than what existed. And maybe by the time the trees are grown, the sediment is back. Nothing is perfect. This is where modeling comes in, and modeling is far from perfect.

In short, I think every situation is different, and there are some places where the tradeoff is worth it and some where it isn't. When for profit consultants get involved I think money can cloud judgement. Like I said modeling isn't perfect and it isn't hard to manipulate. I've seen it first hand on projects worth hundreds of millions of dollars.

 

[pcray1231]

In an area that already lacks trees, though, it's more straightforward. Do the sediment removal and then plant trees.

 

[Fish Sticks]

In an area that already lacks trees, though, it's more straightforward. Do the sediment removal and then plant trees.

Agreed, most of the hammer is treeless above obie road so yea I view that as an opportunity to really plant some trees after even legacy sediment removal implementation. You really have to push back hard to get it though. I have been told ya get thermal improvements from the legacy sediment removal projects but why leave cold water on the table if ya don’t have to ya know?

 

[JeffP]

Agreed, most of the hammer is treeless above obie road so yea I view that as an opportunity to really plant some trees after even legacy sediment removal implementation. You really have to push back hard to get it though. I have been told ya get thermal improvements from the legacy sediment removal projects but why leave cold water on the table if ya don’t have to ya know?

What do you mean push back to get it through? Do you mean the permitting or to get farmers to do it?

 

[Fish Sticks]

What do you mean push back to get it through? Do you mean the permitting or to get farmers to do it?

No sorry to clarify, I mean the people who are prescribing and executing legacy sediment removal are very adamant about shrubbery and not trees. You really have to do a lot of asking about “why would we not do trees for further thermal benefits” and eventually they just kinda say well you could but they have a strong belief a few of the areas they have worked on where historically grasses/shrubs based on seeds found after excavating.

I have always wondered though if things in that gravel basal later found could be reflective of grasses that were growing as a result of timbering and loss of canopy that occurred prior to mill dam construction? We will never get an answer to some of this stuff but I think for thermal benefits no reason we shouldn’t be planting native tree species on these things.

 

[pcray1231]

Best guess is that it's a timing thing. I'm sure you know more than I. Much of the effort in sediment removal appears to be sponsored by the Chesapeake Bay Commission with the stated goal of reducing sediment loading into the bay BY 2025. Whether or not they sponsor the Hammer Creek efforts, those projects are the recent experience of the people doing it.

Grasses/shrubs establish quickly and achieve the swamp/groundwater/stream interaction effect quickly in time for post project monitoring. They can then show pre vs. post project phos, nitrate, turbidity levels and say "look how much good we did, now give us more money to do it elsewhere".

They're not wrong, it has immediate major benefits even without trees. I think long term, wetland suited trees are better. But it probably takes 30+ years and the project professionals just don't really care, they'll be retired by then. Yeah, I'd be in favor of doing the grasses and shrubs and coming along afterwards and putting in saplings within it all. Let nature take it's course from there.

 

[pcray1231]

For those that aren't familiar with this. Shamelessly taken from public documentation of projects.

Typical "before" pic in PA of a stream in need of legacy sediment removal: The brown dirt is accumulated agricultural runoff from years and years of agriculture, mill dams, and the like. You can see on the far bank near the stream, a blacker soil. That's the original soil, the brown soil is deposited on top. The stream cuts a narrow channel down through the brown stuff and gets to the original streambed, but you have unstable banks and lots of siltation in the streambed itself, all being carried downstream too.

And the intended outcome after a project. They take off all of the brown dirt from around the stream and get down to the original gravel/spongy black soil and plant grasses. They basically make a swampy area. As for thermal benefits, remember that this is a swamp with spongy soil. A lot of the water is actually underground.

Same spot during a high water event:

Instead of a fast runoff of chocolate milk, you have a slower, wider wetter swamp filtering through grasses and shrubs, reducing siltation that's carried downstream. And thermal benefits come from more groundwater interaction.

I have zero problem with that approach where it makes sense, mainly in lowland treeless farm areas like the first pic. This is not a high, forested country thing for sure. Lycoflyfisher is correct, not all streams were widely braided meadows. Many piedmont streams, like Hammer, are like this in the headwaters and proceed to flow through forests and hills downstream to take on a more classic trout stream look. Starting with colder, cleaner water with less silt is a good thing. The farmer loses some acreage is why it's tough to do. But yes, in a perfect world I'd plant some willows and wetland resistant trees in that swamp, no doubt. They'll take where they should, and die where they shouldn't.